This invention relates to improved methods and apparatus for drilling wells or other holes in the earth by equipment in which an instrument is carried within the drill string during a drilling operation.
In drilling holes into the earth, it is frequently desirable to monitor one or more conditions in the hole repeatedly during the drilling operation, in order to assist in making decisions as to what steps, if any, should be taken in controlling or altering the drilling procedure. For example, it is often helpful to position in the drill string near the bit an inclinometer probe, which can sense the inclination of the drill string in the earth, and sense the azimuth of that inclination, and transmit the information to a read-out unit at the surface of the earth. Equipment of this general type is disclosed in U.S. Pat. Nos. 3,791,043 and 3,862,499. One inconvenience which has been encountered in the use of such equipment has resided in the loss of time and effort involved in removing the instrument and its flexible suspending line from the drill string each time that another section of pipe is added to the string. Since the flexible line extends out of the drill string at the surface of the earth, it has been thought impossible to connect another pipe section to that end of the string so long as the flexible line is in place. Consequently, the flexible line is normally wound on a drum at the surface of the earth to pull the line and connected instrument from the well, following which the next successive pipe section can be connected to the string and the instrument and flexible line can then be lowered through the added section and into the drill string to the drilling depth.